There is a need to generate X-rays of the type occasioned by the detonation of a nuclear weapon to test the effects of such radiation on various electronic hardware. Such a nuclear detonation results in a electromagnetic pulse (EMP) which can greatly reduce the resistance of semiconductor junctions even when the electronic hardware is located a distance from the detonation, causing such junctions to carbonize due to the vastly increased current through the junctions. As the EMP is spectrum dependent, it is desirable to have the capability of varying the spectrum of the X-rays provided by such generation equipment.
The power weighted mean electron energy necessary for generation of the desired X-rays is at least about 1 MeV. Such a high energy level requires careful design of a diode X-ray source to avoid electrical flashover. Diodes incorporating a pair of anode-cathode gaps in series have been proposed to reduce the electrical stress appearing at a given anode-cathode gap.
One proposed series diode includes a pair of inverse anode-cathodes. By "inverse" is meant that the photons, resulting from electrons crossing the gap and being decelerated by the anode, flow in the opposite direction to the electrons crossing the gap. Each of the cathodes is transparent to the photons in that each is formed by an array of spaced, electrically conductive wires. This diode does not provide a varying spectrum of X-rays because the anode-cathode gaps are not easily adjusted. Furthermore, "transmission" diodes, diodes where the generated photons and electrons crossing the gap both flow in the same direction, are more efficient than inverse diodes above about 500 keV because at that energy level forward scattering of the photons is more dominant. Also with such series diodes various components, such as the cathodes, may need to be replaced after each shot. Such transparent electrodes may require appreciable set-up time thereby reducing the shot rate. For further information concerning the structure and operation of such a series diode, reference may be made to U.S. Pat. No. 4,354,660.